The influence of a rectal ultrasound probe on the separation between prostate and rectum in high-dose-rate brachytherapy.

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The influence of a rectal ultrasound probe on the separation between prostate and rectum in high-dose-rate brachytherapy.

September 9, 2015

The aim of this study was to compare the distance between prostate and rectum as well as rectal dose-volume histogram (DVH) parameters for high-dose-rate (HDR) prostate brachytherapy (BT) with and without a transrectal ultrasound (US) probe in place during delivery.

The study included 20 patients with high-risk prostate cancer treated consecutively with combined external beam radiotherapy (EBRT) and MRI-based HDR-BT. The MRI-based HDR-BT dose plan and prostate gland contour were transferred to the US images after rigid MRI/US coregistration, followed by delineation of the rectum on US images acquired with a transrectal US probe. The prostate-rectum separation was estimated at the apex, reference, and base plane on the US (with rectal probe) and MR images (without rectal probe). Rectal DVH parameters for EBRT + HDR-BT given in equivalent 2 Gy fractionation doses were estimated and compared for US-based and MRI-based HDR-BT dose planning.

MRI-based HDR-BT without a rectal US probe in place as compared with US-based BT with the probe in place demonstrated a significant increase in the prostate-rectum separation, with a potential of reducing rectal dose.